bionic (5) memcache_table.5.gz

Provided by: postfix_3.3.0-1ubuntu0.4_amd64 bug

NAME

       memcache_table - Postfix memcache client configuration

SYNOPSIS

       postmap -q "string" memcache:/etc/postfix/filename

       postmap -q - memcache:/etc/postfix/filename <inputfile

DESCRIPTION

       The  Postfix  mail  system  uses  optional tables for address rewriting or mail routing. These tables are
       usually in dbm or db format.

       Alternatively, lookup tables can be specified as memcache instances.  To use memcache lookups,  define  a
       memcache source as a lookup table in main.cf, for example:

           virtual_alias_maps = memcache:/etc/postfix/memcache-aliases.cf

       The  file /etc/postfix/memcache-aliases.cf has the same format as the Postfix main.cf file, and specifies
       the parameters described below.

       The Postfix memcache client supports the lookup, update, delete and sequence (first/next) operations. The
       sequence operation requires a backup database that supports the operation.

MEMCACHE MAIN PARAMETERS

       memcache (default: inet:localhost:11211)
              The  memcache  server  (note:  singular)  that  Postfix  will try to connect to.  For a TCP server
              specify "inet:" followed by a hostname or address, ":", and a port name  or  number.   Specify  an
              IPv6  address  inside  "[]".   For  a  UNIX-domain  server  specify "unix:" followed by the socket
              pathname. Examples:

                  memcache = inet:memcache.example.com:11211
                  memcache = inet:127.0.0.1:11211
                  memcache = inet:[fc00:8d00:189::3]:11211
                  memcache = unix:/path/to/socket

              NOTE: to access a UNIX-domain socket with the proxymap(8) server, the socket must be accessible by
              the unprivileged postfix user.

       backup (default: undefined)
              An  optional  Postfix  database  that  provides  persistent  backup for the memcache database. The
              Postfix memcache client will update  the  memcache  database  whenever  it  looks  up  or  changes
              information in the persistent database. Specify a Postfix "type:table" database. Examples:

                  # Non-shared postscreen cache.
                  backup = btree:/var/lib/postfix/postscreen_cache_map

                  # Shared postscreen cache for processes on the same host.
                  backup = proxy:btree:/var/lib/postfix/postscreen_cache_map

              Access to remote proxymap servers is under development.

              NOTE  1:  When  sharing  a  persistent  postscreen(8)  or verify(8) cache, disable automatic cache
              cleanup (set *_cache_cleanup_interval  =  0)  except  with  one  Postfix  instance  that  will  be
              responsible for cache cleanup.

              NOTE  2:  When  multiple  tables  share  the  same  memcache  database,  each table should use the
              key_format feature (see below) to prepend its own unique string to  the  lookup  key.   Otherwise,
              automatic postscreen(8) or verify(8) cache cleanup may not work.

              NOTE  3: When the backup database is accessed with "proxy:" lookups, the full backup database name
              (including the "proxy:" prefix) must be specified in  the  proxymap  server's  proxy_read_maps  or
              proxy_write_maps setting (depending on whether the access is read-only or read-write).

       flags (default: 0)
              Optional  flags  that  should  be  stored along with a memcache update. The flags are ignored when
              looking up information.

       ttl (default: 3600)
              The expiration time in seconds of memcache updates.

              NOTE 1: When using a memcache table as postscreen(8) or verify(8) cache without persistent backup,
              specify  a  zero  *_cache_cleanup_interval value with all Postfix instances that use the memcache,
              and specify the largest postscreen(8) *_ttl value or verify(8) *_expire_time value as the memcache
              table's ttl value.

              NOTE  2:  According  to  memcache  protocol  documentation,  a value greater than 30 days (2592000
              seconds) specifies absolute UNIX time. Smaller values are relative to the time of the update.

MEMCACHE KEY PARAMETERS

       key_format (default: %s)
              Format of the lookup and update keys that the  Postfix  memcache  client  sends  to  the  memcache
              server.   By  default,  these  are the same as the lookup and update keys that the memcache client
              receives from Postfix applications.

              NOTE 1: The key_format feature is not used for backup database requests.

              NOTE 2: When multiple tables share the same memcache database, each table should prepend  its  own
              unique  string  to  the lookup key.  Otherwise, automatic postscreen(8) or verify(8) cache cleanup
              may not work.

              Examples:

                  key_format = aliases:%s
                  key_format = verify:%s
                  key_format = postscreen:%s

              The key_format parameter supports the following '%' expansions:

              %%     This is replaced by a literal '%' character.

              %s     This is replaced by the memcache client input key.

              %u     When the input key is an address of the form user@domain, %u is replaced by the SQL  quoted
                     local  part of the address.  Otherwise, %u is replaced by the entire search string.  If the
                     localpart is empty, a lookup is silently suppressed and returns no results  (an  update  is
                     skipped with a warning).

              %d     When the input key is an address of the form user@domain, %d is replaced by the domain part
                     of the address.  Otherwise, a lookup is silently suppressed  and  returns  no  results  (an
                     update is skipped with a warning).

              %[SUD] The  upper-case  equivalents  of  the  above  expansions behave in the key_format parameter
                     identically to their lower-case counter-parts.

              %[1-9] The patterns %1, %2, ... %9 are replaced by the corresponding most significant component of
                     the  input  key's  domain. If the input key is user@mail.example.com, then %1 is com, %2 is
                     example and %3 is mail. If the input key is unqualified or  does  not  have  enough  domain
                     components  to  satisfy  all  the  specified  patterns, a lookup is silently suppressed and
                     returns no results (an update is skipped with a warning).

       domain (default: no domain list)
              This feature can significantly reduce database server load.  Specify a list of domain names, paths
              to  files,  or  "type:table"  databases.   When specified, only fully qualified search keys with a
              *non-empty* localpart and a matching domain  are  eligible  for  lookup  or  update:  bare  'user'
              lookups,  bare domain lookups and "@domain" lookups are silently skipped (updates are skipped with
              a warning).  Example:

                  domain = example.com, hash:/etc/postfix/searchdomains

MEMCACHE ERROR CONTROLS

       data_size_limit (default: 10240)
              The maximal memcache reply data length in bytes.

       line_size_limit (default: 1024)
              The maximal memcache reply line length in bytes.

       max_try (default: 2)
              The number of times to try a memcache command before giving up.   The  memcache  client  does  not
              retry a command when the memcache server accepts no connection.

       retry_pause (default: 1)
              The time in seconds before retrying a failed memcache command.

       timeout (default: 2)
              The time limit for sending a memcache command and for receiving a memcache reply.

BUGS

       The  Postfix  memcache  client cannot be used for security-sensitive tables such as alias_maps (these may
       contain  "|command  and   "/file/name"   destinations),   or   virtual_uid_maps,   virtual_gid_maps   and
       virtual_mailbox_maps  (these specify UNIX process privileges or "/file/name" destinations).  In a typical
       deployment a memcache database is writable by any process that  can  talk  to  the  memcache  server;  in
       contrast, security-sensitive tables must never be writable by the unprivileged Postfix user.

       The  Postfix  memcache  client  requires additional configuration when used as postscreen(8) or verify(8)
       cache.  For details see the backup and ttl parameter discussions in the MEMCACHE MAIN PARAMETERS  section
       above.

SEE ALSO

       postmap(1), Postfix lookup table manager
       postconf(5), configuration parameters

README FILES

       Use "postconf readme_directory" or "postconf html_directory" to locate this information.
       DATABASE_README, Postfix lookup table overview
       MEMCACHE_README, Postfix memcache client guide

LICENSE

       The Secure Mailer license must be distributed with this software.

HISTORY

       Memcache support was introduced with Postfix version 2.9.

AUTHOR(S)

       Wietse Venema
       IBM T.J. Watson Research
       P.O. Box 704
       Yorktown Heights, NY 10598, USA

       Wietse Venema
       Google, Inc.
       111 8th Avenue
       New York, NY 10011, USA

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